Also if not hard, can you tell me about sounds? I mean sound steps when hero moving or hit swords each other, or other sounds. This can be used without rights? Can i found them on youtube or other internet resources for example and use them? Or i need make it by myself? Thanks for help man.

Don't trust what you find on YouTube; you must have all rights to what you put in your Short Film Contest entry. Valve gives you the right to use any of their stuff, but if you want to use a song that's not made by them or you, you must buy the license rights to it, for example. There are some sites out there like freesound.org that make other sound effects available, but you have to be careful because most of its sounds use a license that is not legally compatible. (CC Zero or anything that is just attribution would work, I believe)